Hydrocarbon fluids including crude oils and heavy crude oils contain heteroatoms that should be removed and refined prior to the hydrocarbon being transported or used for commercial consumption. These heteroatoms include compounds containing such elements as sulfur, nitrogen, nickel, vanadium and acidic oxygenates. The heteroatoms may be present in compounds at quantities that negatively impact the refinery processing of the crude oil fractions.
Crude oils that have unsuitable heteroatom properties limit the crude from being economically transported or processed using conventional facilities. These types of crude hydrocarbons may be commonly referred to as “disadvantaged crudes.” Disadvantaged crudes often contain relatively high levels of residue. High residue crudes may be treated at high temperatures to convert the crude to coke. Alternatively, high residue crudes are typically treated with water at high temperatures through the use of steam cracking to produce less viscous crudes and/or crude mixtures. During processing, water removal from the less viscous crudes and/or crude mixtures may be difficult using conventional means.
Disadvantaged crudes may include hydrogen deficient hydrocarbons. When processing hydrogen deficient hydrocarbons using previously known methods, consistent quantities of hydrogen are generally needed to be added, particularly if unsaturated fragments resulting from cracking processes are produced. Hydrogenation during processing, which typically involves the use of an active hydrogenation catalyst, may be needed to inhibit unsaturated fragments from forming coke. Hydrogen is costly to produce and/or costly to transport to treatment facilities.
Disadvantaged crudes often include organically bound heteroatoms (for example, sulfur, oxygen, and nitrogen). Organically bound heteroatoms may, in some situations, have an adverse effect on catalysts. Alkali metal salts and/or alkaline-earth metal salts have been used in processes for desulfurization of residue. These processes tend to result in poor desulfurization efficiency, production of oil insoluble sludge, poor demetallization efficiency, formation of substantially inseparable salt-oil mixtures, utilization of large quantities of hydrogen gas, and/or relatively high hydrogen pressures.
Some processes for improving the quality of crude include adding a diluent to disadvantaged crudes to lower the weight percent of components contributing to the disadvantaged properties. Adding diluent, however, generally increases costs of treating disadvantaged crudes due to the costs of diluent and/or increased costs to handle the disadvantaged crudes. Addition of diluent to disadvantaged crude may, in some situations, decrease stability of such crude.
In the United States and other countries around the world, there has been emphasis by governments to pass stricter standards for hydrocarbon fluid being used commercially that derive from crude oils. For example, in the US, it is strictly required that hydrocarbon fluids, such as on-road diesel fuel, meet the required ultra-low sulfur specifications of 15 ppm sulfur. Due to the extremely low nature of the government imposed specifications, the oil and fuel industry has been continuously evolving their heteroatom removal processes to realize greater and greater heteroatom removal without incurring exorbitant expenses.
One method of removing unwanted heteroatoms from hydrocarbon fluids is through the use of adsorbents or adsorbent beds which attract, bind, separate and remove the heteroatom containing hydrocarbon compounds present in hydrocarbon feeds coming in contact with the adsorbent. The effectiveness of an adsorbent may depend on the adsorbent's binding affinity and ability to attract the heteroatoms in the hydrocarbon fluid. In order to be economical, the heteroatom compound attracted to an adsorbent should be removed from the adsorbent in a manner that allows the adsorbent to be used again. Many adsorbents strongly bind sulfur and other heteroatom compounds, but require high temperatures and severe conditions to both adsorb and to remove the heteroatom compounds, often burning them in the process. Additionally, many refinery products or intermediates cannot be heated to severe temperatures without inducing undesired chemical changes to the hydrocarbon feeds. Thus, there is a need for a new and novel adsorbent capable of binding heteroatoms such as sulfur and nitrogen compounds with a high affinity, yet also capable of easily releasing those heteroatoms at low temperatures and mild conditions.
Advantages of the system and methods described herein over the prior art, include the ability of the adsorbents to be selectively modified and fine-tuned with various alcohol and polyol functional groups attached to the metal complex of the adsorbent, allowing for the adsorbent to have an increased affinity and adsorbing strength for particular characteristics of the heteroatoms being removed from the hydrocarbon feeds as well as selectivity for one or more classes of heteroatoms. The adsorbents of the disclosed system and methods also enjoy an advantage of heteroatom removal from the heteroatom-bound adsorbent at low temperatures and pressures by contacting the heteroatom-bound adsorbent with one or more solvents such as a hydroperoxide or peracid to regenerate the adsorbent at low temperatures and pressures.